1. Field of the Invention
The present invention relates to an apparatus for removing a semiconductor crystal (hereinafter may be referred to as a “semiconductor crystal removal apparatus”), and to a method for producing a semiconductor crystal. More particularly, the present invention relates to a semiconductor crystal removal apparatus in which a semiconductor crystal is removed from a crucible, and to a method for producing a semiconductor crystal.
2. Background Art
Semiconductor crystal production methods include vapor-phase growth methods such as metal-organic chemical vapor deposition (MOCVD) and hydride vapor phase epitaxy (HVPE); molecular beam epitaxy (MBE); and liquid-phase epitaxy. The flux process employing Na flux is a type of liquid-phase epitaxy.
In the flux process, generally, a GaN layer is formed on, for example, a sapphire substrate, to thereby prepare a seed crystal substrate, and a semiconductor single-crystal is grown on the seed crystal substrate in a flux. In this case, the seed crystal substrate, the flux, and a raw material of the semiconductor single-crystal are placed in a crucible, and then the semiconductor single-crystal is grown while temperature and pressure are controlled inside a reaction chamber. Thereafter, the temperature of the reaction chamber is lowered to room temperature. Thus, the flux is solidified through cooling of the reaction chamber to room temperature.
Generally, ethanol treatment or the like is carried out for removing the semiconductor single-crystal from the solidified flux. However, a very long period of time is required for separating the semiconductor single-crystal from the solidified flux through dissolution of the flux by ethanol treatment or the like. Therefore, there has been disclosed a technique in which a crucible is inclined in the interior of a treatment vessel (see FIG. 1, etc. of Patent Document 1). The patent document describes that this technique promotes discharge of hydrogen gas, which would otherwise inhibit ethanol treatment or the like, and enables ethanol treatment or the like to be effectively performed between a semiconductor single-crystal and a flux.    Patent Document 1: Japanese Patent Application Laid-Open (kokai) No. 2010-269967
However, even when the crucible is inclined in the treatment vessel as described in Patent Document 1, the fact remains that the solidified flux is gradually dissolved by a hydroxyl-group-containing treatment liquid such as ethanol; i.e., a long period of time is required for ethanol treatment. In addition, separation of the semiconductor single-crystal from the flux cannot be determined through the aforementioned technique. Therefore, an appropriate operation is required for determining whether or not the semiconductor single-crystal has been separated from the flux.